1. Field of the Invention
This invention relates to a harrow assembly, and is more particularly concerned with an offset wheel or disc harrow designed to be towed by a vehicle in either a working mode or in a transport mode.
2. Description of the Prior Art
Hinge-type offset wheel harrows incorporating gangs of spaced discs are widely known and have been manufactured to incorporate various embodiments and features Due primarily to improvements in towing vehicles such as tractors, there is a trend to manufacture these harrows structurally larger than harrows previously manufactured. While the larger harrows are generally more durable and efficient than the smaller counterparts of the prior art, by increasing the size of disc harrows, various problems are encountered. For example, the disc harrows previously known were generally small enough to permit the drawbar assembly to be manually biased in an operable or in an inoperable position. Further, such a relatively lightweight drawbar could be manually removed from a harrow working position and installed in a harrow transport position. In U.S. Pat. No. 3,460,630 to Richey, the working drawbar is manually biased. The transport drawbar or tongue must be manually removed when the disc harrow is in a working position, and manually installed when the harrow is in a transport position, because the transport drawbar would interfere with the pivoting of the individual harrow units in the working mode. This arrangement is also utilized in an offset disc harrow manufactured by Marchesan under the name Super Tatu.RTM.. Because of the size of the harrow assembly of the present invention, however, the draw bar assemblies used to pull the harrow in either working or transport modes must include large, heavy steel elements which cannot be easily, manually removed and installed or easily, manually biased in an operable or inoperable position. The drawbar assemblies utilized in the prior art, therefore, are not suitable for use in the present invention.
Further, there are various means disclosed in the prior art to permit an offset disc harrow to be towed in a non-working or transport mode. This is advantageous when, for example, it is necessary to move the harrow from one field to another over a road or public highway. U.S. Pat. No. 3,460,630 also discloses a transport means in the form of wheels arranged parallel to and on either side of the entire harrow assembly. Because of the arrangement of the front and rear units of this harrow when collapsed for transportation, however, it is not possible to provide additional transport wheels between the harrow units themselves. The transport means of U.S. Pat. No. 3,460,630 is, therefore, limited in this respect, and is less stable than the present invention when being towed in the transport mode. Similarly, the Marchesan harrow utilizes outer transport wheels only. U.S. Pat. No. 4,308,919 to Coughran discloses another type of disc harrow having transport wheel assemblies. In this reference, however, the wheels are arranged between the individual harrow units only, but are transverse to the harrow units. The harrow assembly, therefore, is towed in the same orientation in the transport mode as the orientation in which it is towed in the working mode. This leads to difficulties when the harrow is being transported on the public highways since the large harrow assemblies of today are often wider than the individual road lanes. Other disc harrows which exemplify the harrows of the prior art are disclosed in U.S. Pat. No. 3,648,781 to Mayer, U.S. Pat. No. 2,931,447 to Kramer, and U.S. Pat. No. 2,860,471 to Welch. Because of the increasingly large structure of today's disc harrows, however, the embodiments previously used to provide transportation means for the disc harrows are less desirable than the structure of the present invention.